“Worse, RCP 8.5 has already been invalidated by choices we have collectively made about green energy, emissions control and population.”

So it is actually mitigation (“emissions control”) which “invalidates” RCP8.5. By extension, without any mitigation RCP8.5 might be a valid projection — quite possibly even on the low side if one would consider only CO2 emissions.

A point of criticism on RCP8.5 is that the net methane emissions are rather high, which impacts CO2-equivalent and it is the reason why the graph shows “>1000ppm CO2eq”.

On the other hand, the RCP8.5 scenario already contains some plausible developments which would happen to limit CO2 emissions even without mitigation policies, such as an increasing role for natural gas and nuclear.

See Riahi et al 2011:

This paper summarizes the main characteristics of the RCP8.5 scenario. The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies.

I agree with Thomas here, presenting RCP8.5 as no-mitigation future is an untrue statement. Please come back and tell you didn’t mean this.

]]>By: Jos Hagelaarshttps://ourchangingclimate.wordpress.com/2016/10/06/earths-temperature-over-the-past-two-million-years-snyder-earth-system-sensitivity/#comment-35031
Sat, 08 Oct 2016 17:46:13 +0000http://ourchangingclimate.wordpress.com/?p=3079#comment-35031– “Why do you treat the Representative Concentration Pathways as projections of potential realities? They are not.”
–“RCP 8.5 has already been invalidated by choices we have collectively made about green energy, emissions control and population.”

To me the RCP’s are clearly described by Bart as “scenario’s” and the RCP8.5 scenario is described as a “no mitigation” scenario.”. Indeed agreements are made about CO2-emission control so hopefully we will not follow that path. But you never know, there are still people in some governments who think climate change is a hoax. And we are still quite close to RCP8.5:

]]>By: thomaswfuller2https://ourchangingclimate.wordpress.com/2016/10/06/earths-temperature-over-the-past-two-million-years-snyder-earth-system-sensitivity/#comment-35030
Sat, 08 Oct 2016 16:47:07 +0000http://ourchangingclimate.wordpress.com/?p=3079#comment-35030Why do you treat the Representative Concentration Pathways as projections of potential realities? They are not.

As I’m sure you are aware, they are ad hoc explanations of possible ways the planet could achieve pre-assigned levels of radiative forcing. Those levels were given as a starting point in the exercise to develop inputs to climate models.

They are not projections. The researchers have specifically said they are not projections for over a decade. A casual look at the ad hoc explanations they came up with show that they are not at all serious, especially RCP 8.5.

Worse, RCP 8.5 has already been invalidated by choices we have collectively made about green energy, emissions control and population.

Only those wishing to foster a sense of panic would hold RCP 8.5 out as either a carrot or stick for influencing policy.